The present invention relates to a semiconductor device and a manufacturing method thereof, and provides a technique that can be applied, for example, to a semiconductor device having a pressure sensor.
Examples of a pressure sensor detecting pressure include, for example, the semiconductor device described in Japanese Unexamined Patent Publication No. 2008-190970. This semiconductor device has a strain gauge over a first surface of a silicon substrate. This strain gauge is formed by diffusing impurities or implanting ions into the first surface of the silicon substrate. A depressed portion is formed in a second surface of the silicon substrate. A part of the silicon substrates, where the strain gauge is formed, is small in thickness, because this depressed portion is formed. In such a structure, when the external pressure varies, a strain is generated in the strain gauge, thereby allowing the resistance of the strain gauge to be changed. The aforementioned pressure sensor detects pressure based on a change in the resistance of the strain gauge.